fix: use includes() check for project placeholder to survive sed substitution (#164)

The CI pipeline runs `sed -i 's/MLAB_PROJECT_PLACEHOLDER/mlab-oti/g'`
to set the production project. The previous strict equality check
`placeholder === 'MLAB_PROJECT_PLACEHOLDER'` became
`'mlab-oti' === 'mlab-oti'` after substitution, which is always true,
causing production to use the mlab-staging fallback.

Using `placeholder.includes('PLACEHOLDER')` instead ensures the check
correctly detects an unsubstituted placeholder while evaluating to false
after sed replaces it with 'mlab-oti'.

This bug has been silently routing all ndt7 tests from the website to
staging infrastructure since the 2026-02-03 release, causing a 99% drop
in ndt7 test data in production BigQuery.

Author: robertodauria

src/js/app.js

@@ -134,7 +134,7 @@ const SpeedTest = {
    */
   mlabProject() {
     const placeholder = 'MLAB_PROJECT_PLACEHOLDER';
-    return placeholder === 'MLAB_PROJECT_PLACEHOLDER' ? 'mlab-staging' : placeholder;
+    return placeholder.includes('PLACEHOLDER') ? 'mlab-staging' : placeholder;
   },
 
   /**